Are prenuptial agreements enforceable in Wisconsin?

Wisconsin uses the Marital Property Act framework, treating prenups as a subset of marital property agreements.

1. Governing Statute

Wis. Stat. § 766.58 governs marital property agreements (which include prenups). Divorce-time equitable-division authority comes from Wis. Stat. § 767.61.

2. Formality Requirements

The agreement must be in writing and signed by both parties (§ 766.58(1)). It is effective on marriage (§ 766.58(7)). Notarization is best practice; no acknowledgment is statutorily required.

3. Voluntariness

Wis. Stat. § 766.58(6) provides defenses: a party may show the agreement was procured by fraud, duress, coercion, or undue influence, or that the party did not voluntarily and knowingly execute it.

4. Disclosure

Section 766.58(6)(b) requires fair and reasonable disclosure of the other party's property and financial obligations, OR a voluntary and express written waiver, OR adequate knowledge.

5. Unconscionability / Inequitable at Divorce

Wisconsin uniquely allows divorce courts to decline to enforce property provisions of a marital property agreement when the court finds the agreement inequitable as to either party at the time of divorce. This is codified at Wis. Stat. § 767.61(3)(L) and gives Wisconsin courts unusually broad equitable discretion to override prenup property provisions.

6. What Cannot Be Waived

Child support and custody cannot be predetermined. Maintenance (alimony) cannot be entirely eliminated by contract in a way the court finds inequitable — § 767.56 maintenance discretion is retained.

7. Key Wisconsin Case Law

Button v. Button, 131 Wis. 2d 84 (1986) (foundational disclosure standard); Hengel v. Hengel, 122 Wis. 2d 737 (Ct. App. 1985); Greenwald v. Greenwald, 154 Wis. 2d 767 (Ct. App. 1990).

This is legal information, not legal advice.